The goal is to develop an automated prescreening system for gynecological cytology specimens. A multidimensional slit-scan flow system was developed to serve as an automated prescreening instrument for gynecological cytology. A single blind clinical study was carried out to evaluate system performance. Cellular material was collected by scraping the uterine cervix and stained in suspension with acridine orange. We analyzed 856 specimens including 195 abnormal specimens representing a broad spectrum of abnormality. Approximately 50,000 cells were analyzed for each specimen. The system false positive rate was 17%, while the false negative rate was 3.9%. All misclassified abnormals were specimens with cellular changes consistent with a slight dysplasia of nonkeratinizing type. The instrument in its present configuration appeared sensitive to the entire spectrum of abnormality existing in the female genital tract and classified as abnormal any specimen containing on the order of 0.1% (or greater) abnormal cells. An alternate system has been fabricated to provide similar multidimensional slit-scan information from a less complex instrument. This two-station instrument provides a conventional one-dimensional slit-scan measurement station followed by a three-dimensional measurement station that provides a "second look" at any desired cell. Parallel microprocessor contour processing electronics have been fabricated and system testing is in progress. (3)